Pre-eclampsia is a pregnancy-specific disorder characterized by hypertension and proteinuria observed after the 20th week of gestation. It affects 5-8% of U.S. pregnancies, is a precursor for potentially fatal eclampsia, and is a leading global cause of maternal and infant morbidity. The incidence of pre-eclampsia has increased by nearly one-third over the past decade and hypertensive disorders during pregnancy are now responsible for at least 76,000 U.S. deaths each year. The cause of pre-eclampsia and its rising incidence remain uncertain. However, several lines of evidence suggest that sleep-disordered breathing (SDB) could play a role. SDB is common, most often undiagnosed - especially in women - and treatable. Snoring, the hallmark symptom of SDB, is more frequent during pregnancy. Increased weight promotes SDB, and significant weight gain or other physiological changes during pregnancy also may exacerbate SDB. SDB has been associated with elimination or reversal of normal nocturnal dips in blood pressure (BP), similar to BP patterns observed in pre-eclampsia. Of note, SDB is a known independent risk factor for hypertension in non-pregnant adults but it is unknown if SDB in pregnant women contributes to pre-eclampsia. Treatment of SDB with CPAP has been shown to ameliorate nocturnal BP increases in hypertensive patients with SDB, but not in hypertensive patients without SDB. No study has determined whether SDB does in fact increase nocturnal BP during pregnancy and whether SDB promotes pre-eclampsia remains unproven. Therefore, the main goals of this research are to identify whether SDB - as measured by overnight polysomnography - is associated with pre-eclampsia, to confirm that use of auto-titrating positive airway pressure (auto-PAP) can improve nocturnal BP, and to determine whether any such effect depends on the presence of underlying SDB. Moreover, we will show that such improvement in nocturnal BP will be associated with improved maternal daytime BP and improved fetal outcome, as measured by more days in utero and fewer admissions to the neonatal intensive care unit. RELEVANCE (See instructions): This novel research will show that treatment of sleep-disordered breathing in women with pre-eclampsia - a serious complication of pregnancy - will reduce maternal blood pressure which will, in turn, result in improved health for mothers and babies. (End of Abstract)